Modular flow systems are common to process-related industries. For example, stream selecting/switching systems are commonly used in the analytical instrumentation market to route different fluids from multiple sources to a single analyzer. Often, a single automated process analyzer is used for analyzing multiple sample streams. Since automated process analyzers are expensive, using a single analyzer significantly reduces the cost of analyzing multiple gas and liquid sample streams in petrochemical plants, refineries and other process-related industries.
Sample streams are generally transported to a stream selecting/switching system by tubing or piping. The stream selecting/switching system selects a single sample stream from the multiple samples streams and routes the single stream to the analyzer. The number of sample streams and the desired system configuration can vary greatly depending on the industry and application. As a result, modular systems are preferred because they provide increased flexibility in customizing the system.
Modular stream selectors are commonly constructed of multiple valve assembly/base combinations or modules. A valve assembly is typically fastened to a base that contains a flow path for fluid to travel to the analyzer. The valve assembly can route a sample stream to the analyzer via the base. Multiple bases can connect to form a common flow path to the analyzer. To ensure a fluid tight attachment between two bases, seals are positioned between the bases and a method for applying force to the seals is used. Tie rods (a threaded rod with nuts on either end) are commonly used to connect the multiple bases together and apply force to the seals. With tie rods, an appropriate length tie rod must be selected based on the number of bases to be attached and all of the seal connections between the bases are formed at the same time as the tie rod is tighten down.
Another known approach to connecting multiple bases in a modular stream selector utilizes custom bolts that have both a male threaded end and a female threaded end. The bolts are threaded together such that the male end of one bolt threads into the female end of a second bolt. An example of this approach can be found in U.S. Pat. No. 6,619,321 B2. As the bolts are threaded into each other, equal torque is applied to each threaded joint. Thus, when a user attempts to remove the bolts in reverse order, a threaded joint may be loosened other than the threaded joint desired.